1. Field of the Invention
The present invention is related to an antenna structure, and more particularly, to an antenna having wider bandwidth.
2. Description of Related Art
With rapid progress of Internet technologies, plenty of services related to Internet, including the Internet services for work and daily life, have been provided for people nowadays. In the initial stage, the networks of Internet are all wired. Users need to deploy network cables before connecting to Internet. That is very inconvenient, especially when there are a lot of people who need to connect to Internet together. For example, in offices or schools, deploying networks cables needs a lot of time and labor. Besides, the networks cables deployed are usually very close and numerous, usually like spider's webs. The networks cables are hard to be put in order and usually do not have a good appearance. However, with occurrence of wireless local area networks (LANs), the drawbacks of the network deployment mentioned above are removed gradually. In the wireless LAN technologies, data are transferred in a wireless manner via antennas. Without disposition of antennas, wireless network devices, such as Access Points (AP) or client of networks, cannot transmit or receive data. Hence, antennas play an important role in the wireless LAN technologies.
Conventional inverted F antennas have a compact size and a simple structure and are easy to design. Hence, in recent years, inverted F antennas are applied extensively to various communication systems and products. In the wireless LAN technologies, inverted F antennas are often used. In order to adapt to different countries' wireless LAN standards, which use different frequency bands, the inverted F antennas used in wireless LANs are designed to occupy different frequency bands accordingly, such as 5.15-5.35 GHz or 5.47-5.725 GHz.
However, the frequency bands of the inverted F antennas are very narrow. For a user who goes aboard frequently and needs to connect to Internet via wireless LANs, he usually needs to change antennas properly to adapt to local frequency band requirements because the frequency bands used for wireless LANs in different countries are usually different. The user can access the local wireless LANs only when he uses a proper antenna. If he doesn't do so, he cannot access the local wireless LANs even if he stays in a place with wireless LAN services. That is very inconvenient for people who usually go aboard.
Conventionally, if an inverted F antenna's frequency band for data transmission needs to cover multiple frequency bands used in different areas, for example, ranging from 5.15 GHz to 5.825 Ghz or larger, the design difficulty will increase considerably due to the structural limitation of the inverted F antenna.
Therefore, the present invention provides an antenna structure, especially suitable to be applied for embedded antennas of AP. It has wider bandwidth and its frequency band sufficiently covers the frequency band used in Japan and Europe and the Federal Communications Commission (FCC) frequency band used in United States, i.e. ranging from 4.9 GHz to 5.85 GHz or 5.9 GHz. In this way, the present invention increases the applicable area and convenience for users and thus resolves the problems of the prior art mentioned above.